Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Human or animal hair includes a cuticle that is the outermost part of the hair shaft. The hair cuticle is a hard shingle-like layer that provides the mechanical strength of the hair fiber and acts as a protective barrier for the hair softer inner structure including the medulla and cortex. A healthy cuticle provides not only a protective layer but also a structure that controls the moisture content of the hair fiber. The most of the shine or luster that makes healthy hair so attractive is maintained due to the cuticle. Such cuticles are often damaged by external mechanical treatment such as brushing, using heat or chemical processing. Also, environmental elements such as the sun or wind can cause wear and tear on the hair cuticles.
Accordingly, the cuticle condition of hair determines the health and cosmetic problems of the hair because the capability of hair for retaining its inner content and shine can be deteriorated when the cuticle is damaged through exposure to hair treatment and exposure to the natural environment. Accordingly, it is important to precisely measure the shine or luster of the hair cuticle to determine the overall health of hair so that one can assess possible cosmetic options and hair care options to maintain or improve the health of the hair. Also, the hair condition measurement will be desirable for all cosmetic applications including formulation, support of efficacy claim and efficacy testing of hair care products.
Hair condition measuring devices have been developed to detect the moisture content in hair, and have employed various techniques including a NIR (near infrared) moisture meter and Raman spectroscopy. The NIR moisture meter relies on the property of water that absorbs a specific wavelength of NIR light. However, it may be difficult to precisely measure the attenuation of the NIR light reflected from thin and fine hairs. Also, different levels of moisture at the surface and inner side of hair make the moisture measurement more challenging. The Raman spectroscopy relies on inelastic scattering of monochromatic light such as laser light irradiated on molecules of moisture in hair. For example, the laser light interacts with molecular vibrations, resulting in the energy of the laser photons being shifted upwards or downwards between a ground energy state and a virtual energy state. The shift in energy provides information about the vibrational modes to identify the molecules of moisture. Although the Raman spectroscopy provides decent precision of hair condition measurement, it is costly and may not be implemented in a portable size for individual users.